It is both extremely time-consuming and difficult to remove residues of material from the flow channel of an extrusion press when the mixture in the press is to be changed or when a production run has been completed. It is usually necessary to detach and extract each scrap of material remaining in the flow channel by hand or by using tools. This is very time-consuming and it will be apparent that, in any production process which necessitates several changes of mixture, the process is interrupted for long periods of time. Moreover, when the material residues are removed using tools, the extremely smooth walls of the flow channels often become scored. This necessitates the extensive regrinding of the walls of the flow channel.
U.S. Pat. Spec. No. 3,653,419 discloses a filter changing means which includes a frame which is disposed at right angles to the direction of flow of the material. The frame accommodates two sets of filters and is displaceable so that, at any given time, one set of filters is disposed in the flow channel for filtering purposes and the other set are not in use. Changeover of the sets of filters permits a contaminated set of filters to be taken out of use for cleaning and/or replacement. However, such an arrangement does not suggest any way in which material residues can be removed from the interior of the press.